White oil stabilizer



United States Patent ware No Drawing. Filed May 23, 1960, gel. No.31,222

3 Claims. (31. 2s2- 3 This invention relates to improved hydrocarbon oilcompositions. More particularly, this invention relates to white mineraloils containing a small amount of 110- Inogeneously dispersed zinc2-ethylhexoate capable of beneficially inhibiting the development ofodor and haze normally occurring upon exposure of the oil to sunlight.

The oils contemplated as most suitable for use in accordance with ourinvention are generally known as highly refined, industrial type whitemineral oils and are available commercially in various grades differingchiefly with respect to viscosity properties. When initially producedfrom their source, namely, crude oil stocks, they are transparent,colorless and substantially odorless oily liquids. Either paraffin-basecrudes, naphthene-base crudes or mixtures of said crudes may be employedin obtaining the White mineral oil. Although the quality of the finishedproduct depends primarily upon the degree of care and skill employed inthe refining process, certain of its basic properties are determined bythe type of crude used. For example, a naphthene-base crude provides awhite mineral oil of relatively high specific gravity and viscositycharacteristics. On the other hand, a Pennsylvania type paraffin-basecrude yields a white oil of generally lower viscosity properties andspecific gravity. In addition to the physical properties noted for thevarious mineral oils derived from the particular sources mentioned,these crudes also yield oils differing somewhat in other properties. Forexample, white oils derived from parafiin-base crudes exhibit excellentheat resistance and are noted for their affinity for certain waxes.Particularly because of the latter mentioned attribute, an oil of thistype is favored in certain applications such as for example in thepreparation of cosmetic formulations.

. The first step in the production of white oil consists in the removalof the lighter portions of the crude such as gasoline, naphtha, keroseneand certain like fractions such as for example fuel oils. Thissegregation of the enumerated fractions is customarily accomplished by aheat process referred to as fractional distillation. After the lighterfractions of the crude have been separated as indicated, the oil residueis further distilled. The lower boiling fractions of said residue serveas the raw oil from which the white oils are ultimately obtained via arefining operation.

The primary purpose in refining the raw oil fractions is to removevarious reactive and unsaturated hydrocarbons and impurities therefrom,which components are responsible for the color, odor, taste and otherobjectionable properties normally associated with the unrefined oil.Although the specific details of the refining procedure may varyconsiderably among the individual manufacturers of the white oil, itwill almost always include treatment of the oil with sulfuric acid,washing with alkalies and solvents, and the application of adsorbents.

The purpose of the sulfuric acid treatment is to remove all of theunsaturated, aromatic and other reactive hydrocarbons and most of theimpurities that are present in the oil. The action of the treating acidis both chemical and a physical one. In its chemical role, the sulfuricacid reacts with a large proportion of the objectionable componentspresent to yield complexes capable of ready removal. The acidadditionally serves as a solvent for the said reaction products orcomplexes and. also effects removal of resinous and asphaltic substancesand other like impurities from the oil.

In most of the refining practices the oil is treated with largequantities of either concentrated or fuming sulfuric acid (oleum). Thequantity and concentration of acid used, the temperature, the length oftreatment and the method of application depends upon the type of crudeused and the type of oil and degree of refinement required. Ordinarily,30 to 70% of acid based on the weight of the oil is used. The contacttime of acid with oil varies extensively as indicated and ranges from asbrief as a few minutes in continuous treating to about one hour in batchprocesses.

Following the acid treatment, the oil is usually further refined by somesort of adsorption process in order to remove minute traces of carbon,coke, resinous and asphaltic substances, coloring matter, moisture, etc.The commonly used adsorbents are of mineral origin and include fullersearths in natural state or in acid-activated form, e.g., bauxite,bentonite, etc. Adsorbents of organic origin such as charcoal, activatedcarbon and the like as well as such substances as silica gel, aluminagel or similar synthetic adsorbents are also used.

White mineral oils are employed in a legion of industrial applications.The particular application involved more or less dictates the grade ofmineral oil to be used, especially as regards its viscositycharacteristics. Accordingly, one can find numerous commercial productsgenerally sold to meet relatively narrow viscosity specifications. Thusone may readily avail of proprietary products ranging in viscosity fromas low as 30 SSU units Saybolt at F. to a viscosity of as high 500 SSU.Of this broad range of viscosities that may be found in products of thistype, there are two general classifications, namely, light viscosity orsimply light white mineral oils, i.e., those having a Saybolt viscosityof not more than about SSU at 100 F. and heavy white mineral oils whichhave higher viscosity than that specifically stated. Details withrespect to the aforesaid viscosity characterization of oil products maybe found in ASTM test D445- 46T.

Apart from lubricating applications which usually include mostlubricants for food processing apparatus wherein a medicinal grade ofoil is required, there are many other type applications in which aso-called technical grade of white mineral oil is perfectlysatisfactory. The technical grade designation connotes an oil which ishighly refined and substantially chemically inert, but not so absolutelyinert as to permit use for medicinal purposes as an internal lubricant.The technical grade oils are used extensively in cotton processing,leather dressings, and especially in the preparation of cosmetics orcosmetic bases, such as makeup preparations, cold creams, hairpreparations and the like. Our invention especially pertains totechnical grade white mineral oils useful in the latter applicationsamong others of a similar nature.

It is known that all white mineral oils, however fully refined, have atendency to deteriorate with a development of haze and odor whichdevelopment is greatly accelerated upon exposure of the oil to light,particularly at elevated temperatures. The odor experienced is that of adisagreeable hydrogen sulfide odor and although while the amounts ofhydrogen sulfide generated in such a deterioration process are extremelysmall they are nevertheless perceptibly obnoxious.

We have found that when the substance zinc 2-ethylhexoate is added torefined white mineral oils in relatively minute quantities, the oil isinhibited towards the formation of hydrogen sulfide and hazedevelopment. As mentioned previously, the deterioration or formation ofhydrogen sulfide and haziness is known to be contributed to andaggravated by exposure of the oil to actinic radiation. Accordingly, itwas most surprising to find that zinc 2-ethylhexoate when contained in awhite mineral oil in the contemplated minute quantities has the abilityto effectively adsorb ultraviolet light; for this appears to be theprocess by which the degenerative eifects of the incident actinic lightare principally thwarted. Nevertheless, we believe that the function ofthe zinc soap extends beyond mere ultraviolet light adsorption becausewe have employed substituted benzophenone light adsorbers exhibitinghigh ultraviolet adsorbtion characteristics and have found that theywere not nearly as eifective in retarding deterioration of the whitemineral oil as our stabilizer.

The zinc soap useful in the practice of our invention is admirablyadapted for the purposes intended because the compound itself isodorless, substantially colorless, practically nontoxic, readily solublein the white oil and at the same time considerably more stable towardoxidation and deterioration upon aging and exposure to light and heatthan the white oil itself which obviously is a fundamental prerequisitefor an inhibitor of this type.

The amount of zinc 2-ethylhexoate that can be added to the white mineraloil in order to achieve effective protection ranges from as low as 50p.p.m. based on the oil. The preferred range of the additive extendsfrom about 100 to 1000 p.p.m. Amounts greater than 1000 p.p.m. can beused but the extent of improvement in stabilization to be realized inusing these higher amounts is not economically warranted.

Incorporation of the zinc soap into the white oil poses no problem andit can be incorporated therein by moderate stirring of the twocomponents, shaking, etc.

In order to further illustrate the nature of this invention, thefollowing example is given in which all parts are parts by weight. Thisexample is not to be construed as limitative of the invention since theonly limitations intended are those expressed in the appended claims.

EXAMPLE I Into portions of a white mineral oil having a Sayboltviscosity of 70 SSU at 100 F. was added zinc 2-ethylhexoate (22% zinccontent) in concentrations ranging from 125 to 1000 p.p.m. based on theweight of the oil.

42 The samples were stirred in order to effect solution of the zinc soapin the oil and then exposed in the glass bottles to direct sunlight fora number of days along with an untreated sample of the same oil. Thesamples were observed for development of hydrogen sulfide and haze atdaily intervals. The results of these experiments are tabulated in TableI below.

What is claimed is:

1. A composition of matter consisting essentially of a colorless andodorless white mineral oil free of unsaturated and aromatic hydrocarbonscontaining from about 0.005 to 0.1% of zincl-ethylhexoate.

2. A composition of matter consisting essentially of a colorless andodorless white mineral oil free of unsaturated and aromatic hydrocarbonshaving a Saybolt viscosity of less than about 170 SSU at 100 F.containing from about 0.005% to 0.1% of zinc 2-ethylhexoate.

3. A composition of matter consisting essentially of a colorless andodorless white mineral oil free of unsaturated and aromatic hydrocarbonshaving a Saybolt viscosity of about SSU at F. containing from about0.005 to 0.1% of zinc Z-ethylhexoate.

References Cited in the file of this patent UNITED STATES PATENTS2,001,108 Parker May 14, 1935 2,345,580 Buxton Apr. 4, 1944 2,363,722Faust Nov. 28, 1944 2,384,551 Jehle Sept. 11, 1945 2,628,195 Allison eta1 Feb. 10, 1953 2,671,758 Vinograd et al Mar. 9, 1954

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A COLORLESS ANDODORLESS WHITE MINERAL OIL FREE OF UNSATURATED AND AROMATIC HYDROCARBONSCONTAINING FROM ABOUT 0.005% TO 0.1% OF ZINC 2-ETHYLHEXOATE.